In prestressed concrete, if there remains void in the grouting inside a sheath due to defective construction work, then there are times when a fracture develops in a prestressed concrete (PC) cable at the position of the void. The sound generated when a fracture develops in the PC cable can be detected using an acoustic emission (AE) sensor. Moreover, for a short while after the fracture has developed, the frictional sound attributed to sliding and refitting of the cable and grout can also be detected using the AE sensor.
The phenomenon of developing a fracture in the PC cable inside the prestressed concrete happens in a flash and in an unexpected manner. However, in the conventional technology, after the PC cable refits in a stable state, there is no detection of any abnormality indicating that the prestressed concrete has become weaker in strength. For that reason, the AE sensor needs to be kept operational on a constant basis.